The renewal application for this project will follow-up the findings of the parent grant and previous studies which suggest: 1) African-Americans have an impaired natriuretic response to stress; 2) this pattern is related to the functioning of the renin-angiotensin-aldosterone system; and 3) is associated with the early development of target organ damage. In addition, these studies 4) indicate increased adiposity contributes to the pattern. Specific Aims 1 and 2 will examine the effects of an angiotensin receptor blocker on the pressure natriuresis response to stress in African-Americans with impaired stress-induced pressure natriuresis, confirming the role of angiotensin II in the response pattern. Furthermore, this effect will be compared in normal weight versus overweight individuals, with a hypothesized greater effect in overweight subjects. Aim 3 will compare the effects of an angiotensin receptor blocker between carriers and noncarriers of a functional polymorphism of the angiotensin II receptor type 1 gene. These results will provide additional evidence for the mechanistic role of angiotensin II and continue our gene/environmental approach to the study of mechanisms underlying the development of hypertension. Our fourth and final aim is to test the hypothesis that individuals who displayed impaired stress-induced pressure natriuresis on initial testing will display greater increases in blood pressure and related target organ damage than those who displayed normal stress-induced pressure natriuresis. This follow-up study will provide more direct evidence of the clinical significance of impaired stress-induced pressure natriuresis. Relevance to public health: High blood pressure, or hypertension, remains a significant health problem in industrialized nations. The problem is particularly significant in the African-American population in whom "impaired" sodium regulation plays an important role. The results of this study will help further define the interactive effects of genetic predisposition and environmental stress on sodium handling in the development of hypertension, particularly in overweight African-Americans. The pharmacologic interventions will also provide evidence for effective management of this potentially clinically significant response pattern.